Rubber-based structural white-shell adhesives

ABSTRACT

One-component hot-curing structural adhesives based on liquid rubbers, which may optionally contain functional groups, solid rubbers, thermoplastic polymer powders and sulfur and also vulcanization accelerators are suitable for bonding metal parts. Tensile shear strengths of more than 15 MPa and high breaking elongations of more than 15% can be obtained. These adhesives are substantially free from low molecular weight epoxy resins and are particularly suitable for use in white-shell assembly in the car industry.

This invention relates to one-component, hot-curing compositions basedon liquid rubbers and fine-particle powder-form thermoplastic polymersand to their production and use as structural adhesives with a breakingelongation of more than 15%.

BACKGROUND OF THE INVENTION

In modern assembly techniques for joining metal components in machineconstruction, vehicle or equipment manufacture, more especially in carmanufacture, conventional methods of fixing, such as riveting, screwingor welding, are being increasingly replaced by bonding. Spot weldingabove all, which is a source of future corrosion, is being displaced asfar as possible or is being applied in combination with structuraladhesives. For this reason, there is an increased demand forhigh-strength structural adhesives. For assembly reasons, theseadhesives have to be used at the so-called white-shell stage of carmanufacture, i.e. the adhesives are generally applied to the uncleanedmetal surface. These surfaces are often coated with variouscorrosion-inhibiting oils and drawing oils, so that the adhesives usedthere should not be functionally affected by these oils. In addition,the adhesives should be capable of withstanding--preferably withoutpregelation--the various washing baths and installations and the hightemperatures of up to around 240° C. prevailing in the baking ovens forelectrocoating and should also cure at temperatures of that order.Moreover, the adhesives are required to exhibit good ageing-resistantadhesion to various galvanized steels, for example electrolyticallygalvanized steel plates, hot-dip galvanized steel plates and thecorresponding galvannealed steel plates or galvanized and subsequentlyphosphated steel plates. Structural adhesives for these applicationsmust also have a minimum strength of about 15 MPa. In the interests ofsmooth assembly line operation, only one-component materials capable ofbeing transported by pumps and applied by machine are suitable.

On account of the demanding strength requirements, one-componenthot-curing epoxy adhesives have mainly been used for these applicationsin the past. Apart from the advantages of high tensile strength,however, epoxy adhesives have a number of major disadvantages. Thepaste-like, hot-curing one-component epoxy adhesives do not showadequate resistance to washing in the washing and phosphating baths, sothat the corresponding bonds normally have to be pregelled by inductionheating or in special ovens. Unfortunately, this involves an additionalstep. Attempts have been made to overcome this by developingone-component hot-curing epoxy adhesives resembling hotmelts incharacter. Unfortunately, these adhesives require special applicationsystems because they have to be applied hot. Another generaldisadvantage of epoxy adhesives is their tendency to absorb moistureunder the effect of high atmospheric humidity which can lead tocorrosion phenomena and weakening of the bond in the bond line. Althoughepoxy adhesives are distinguished by high tensile strength, theirbreaking elongation is generally very poor; even epoxy adhesivesflexibilized by addition of rubber have a breaking elongation of lessthan 5%. In addition, the use of epoxy adhesives based on low molecularweight epoxy compounds (molecular weight<700) is undesirable onindustrial hygiene grounds because these low molecular weight epoxycompounds can initiate allergic or sensitizing reactions on contact withthe skin.

For some time, compositions based on vulcanizable rubbers have been usedas an alternative. EP-B-97 394 describes an adhesive mixture based on aliquid polybutadiene rubber, powder-form sulfur, organic acceleratorsand optionally solid rubber. According to B. D. Ludbrook, Int. J.Adhesion and Adhesives, Vol. 4, No. 4, pages 148-150, correspondingadhesives based on liquid polybutadienes are capable of attainingstrength levels equivalent to those of flexibilized epoxy adhesivesthrough an appropriate choice of the quantity of sulfur andaccelerators. Whereas these formulations have good curing properties andshow high resistance to ageing and even adhere acceptably to normaloiled steel plate, their usefulness for various galvanized steel platesis limited, in addition to which the breaking elongation of thesehigh-strength rubber adhesives is very poor.

To improve adhesion, DE-C-38 34 818 proposes using OH-terminatedpolybutadienes for the liquid rubber. According to EP-B-441 244,homopolymers or copolymers containing thiol, amino, amido, carboxyl,epoxy, isocyanate, anhydride or acetoxy groups may be used in additionto hydroxyfunctional homopolymers or copolymers as the functional rubberpolymer, although the cured adhesive mixture has a breaking elongationof no more than 15%.

According to EP-B-309 903 and DE-C-40 27 064, polyfunctional epoxycompounds may be added to the adhesive mixtures based on liquid rubbersto improved adhesion and tensile shear strength. Apart from the factthat it is undesirable for the reasons explained above to use adhesivecompositions containing epoxy resin, the adhesive compositions disclosedin the last two documents are not suitable as structural adhesivesbecause they only reach a very low strength level of at most 3 MPa.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Not applicable.

DETAILED DESCRIPTION OF THE INVENTION

Accordingly, the problem addressed by the present invention was toprovide adhesives and sealants which could be used with advantage forjoining metal parts in automobile shells ("white shells") and which

would show adequate permanent adhesion on a number of the metal surfacesused today without any need for cleaning pretreatments,

could be used as structural adhesives (structural adhesives in thecontext of the invention being adhesives which attain a strength of atleast 15 MPa in tensile shear tests),

would have a breaking elongation according to DIN 53504 of more than 15%and preferably more than 20%, in addition to which

the materials would comprise one component, would be hot-curing andwould cure at temperatures of 160° C. to 240° C., their strengthproperties not being significantly affected by the curing temperature.

Apart from normal oiled steel plates, substrates on which adhesion mustbe obtained include, in particular, the various galvanized and oiledsteel plates and aluminium.

According to B. D. Ludbrook loc. cit., the strength values ofrubber-vulcanized adhesives can be significantly increased by thequantity of sulfur and accelerator, but always to the detriment ofbreaking elongation. It has surprisingly been found that the addition offine-particle powders of thermoplastic polymers to adhesives based onliquid rubbers not only increases tensile shear strength, it alsosignificantly improves breaking elongation. Since the other properties,for example ageing resistance and adhesive behavior on the substratesmentioned above, are not affected by the addition of the thermoplasticpolymer powder, the adhesives in question are very much more universalin their usefulness. Thus, structural adhesives may even used for thefirst time where, hitherto, it has only been possible to use adhesiveswith lower strength levels on account of the high elasticity required,as is the case for example with lining adhesives for bonding innerpanels to outer panels in car manufacture where high torsional rigidityis required for structural reasons.

The adhesive/sealant compositions according to the invention contain atleast one of the following substances:

one or more liquid rubbers and/or solid rubbers or elastomers

fine-particle powders of thermoplastic polymers

vulcanization agents, vulcanization accelerators, catalysts

fillers

tackifiers and/or primers

extender oils

antiagers

flow aids.

Liquid rubbers or elastomers may be selected from the following group ofhomopolymers and/or copolymers:

Polybutadienes, more particularly 1,4- and 1,2-polybutadienes,polybutenes, polyisobutylenes, 1,4- and 3,4-polyisoprenes,styrene/butadiene copolymers, butadiene/acrylonitrile copolymers; thesepolymers may have terminal and/or (statistically distributed) lateralfunctional groups. Examples of such functional groups are hydroxy,amino, carboxyl, carboxylic anhydride or epoxy groups. The molecularweight of these liquid rubbers is typically below 20,000 and preferablybetween 900 and 10,000. The percentage content of liquid rubber in thecomposition as a whole depends upon the required rheology of the uncuredcomposition and the required mechanical properties of the curedcomposition. The percentage content of liquid rubber or elastomernormally varies between 5 and 50% by weight, based on the formulation asa whole. It has proved to be useful in this regard to employ mixtures ofliquid rubbers differing both in their molecular weight and in theirconfiguration in relation to the remaining double bonds. To achieveoptimal adhesion on various substrates, a liquid rubber componentcontaining hydroxyl groups or anhydride groups is used in theparticularly preferred formulations. At least one of the liquid rubbersshould have a high percentage content of cis-1,4-double bonds whileanother liquid rubber should have a high percentage of vinyl doublebonds.

By comparison with liquid rubbers, suitable solid rubbers have asignificantly higher molecular weight (MW=100,000 or higher). Examplesof suitable rubbers are polybutadiene, preferably with a very highpercentage of cis-1,4-double bonds (typically above 95%),styrene/butadiene rubber, butadiene/acrylonitrile rubber, synthetic ornatural isoprene rubber, butyl rubber or polyurethane rubber.

The addition of fine-particle thermoplastic polymer powders produces asignificant improvement in tensile shear strength while maintaining avery high breaking elongation hitherto untypical of structuraladhesives. Thus, tensile shear strengths of more than 15 MPa can beachieved for breaking elongations well above 15% and, very often, above20%. The high-strength structural adhesives hitherto typically used werebased on epoxy resins which only have breaking elongations of less than5%, even as flexibilized adhesive formulations. The combination of hightensile shear strength values with high breaking elongation isattributed to the addition of thermoplastic polymer powders inaccordance with the invention. According to the invention, numerousthermoplastic polymer powders are suitable additives, including forexample vinyl acetate either in the form of a homopolymer or in the formof a copolymer with ethylene and other olefins and acrylic acidderivatives, polyvinyl chloride, vinyl chloride/vinyl acetatecopolymers, styrene copolymers of the type described, for example, inDE-A-40 34 725, polymethyl methacrylate and copolymers thereof withother (meth)acrylates and functional comonomers, for example of the typedescribed in DE-C-24 54 235, or polyvinyl acetals, for example polyvinylbutyral. Although the particle size or rather particle size distributionof the polymer powders does not appear to be particularly critical, theaverage particle size should be below 1 mm, preferably below 350 μm and,more preferably, between 100 and 20 μm. Polyvinyl acetate and copolymersbased on ethylene/vinyl acetate (EVA) are most particularly preferred.The quantity of thermoplastic polymer powder added is determined by therequired strength range and is between 2 and 20% by weight, based on thecomposition as a whole, a particularly preferred range being from 10 to15%.

Since the crosslinking or curing reaction of the rubber composition hasa critical influence on the tensile shear strength and breakingelongation of the cured adhesive composition, the vulcanization systemhas to be selected and adapted with particular care. Variousvulcanization systems based on elemental sulfur and vulcanizationsystems with no free sulfur may be used. Vulcanization systems with nofree sulfur include those based on thiuram disulfides, organicperoxides, polyfunctional amines, quinones, p-benzoquinone dioxime,p-nitrosobenzene and dinitrosobenzene and also systems crosslinked with(blocked) diisocyanates. Vulcanization systems based on elemental sulfurand organic vulcanization accelerators and also zinc compounds are mostparticularly preferred. The powder-form sulfur is used in quantities of4 to 15% by weight, based on the composition as a whole, quantities of 6to 8% being particularly preferred. Suitable organic accelerators arethe dithiocarbamates (in the form of their ammonium or metal salts),xanthogenates, thiuram compounds (monosulfides and disulfides), thiazolecompounds, aldehyde/amine accelerators (for examplehexamethylenetetramine) and also guanidine accelerators, dibenzothiazyldisulfide (MBTS) being most particularly preferred. These organicaccelerators are used in quantities of 2 to 8% by weight, based on theformulation as a whole, and preferably in quantities of 3 to 6%. In thecase of zinc compounds acting as accelerators, a choice may be madebetween the zinc salts of fatty acids, zinc dithiocarbamates, basic zinccarbonates and, in particular, fine-particle zinc oxide. The content ofzinc compounds is in the range from 1 to 10% by weight and preferably inthe range from 3 to 7% by weight. In addition, other typical rubbervulcanization agents, for example fatty acids (for example stearicacid), may be present in the formulation.

Although, in general, the compositions according to the inventionalready show very good adhesion to the substrates to be bonded by virtueof the presence of liquid rubber containing functional groups,tackifiers and/or primers may be added where necessary. Suitabletackifiers and/or primers are, for example, hydrocarbon resins, phenolicresins, terpene/phenol resins, resorcinol resins or derivatives thereof,modified or unmodified resinic acids or esters (abietic acidderivatives), polyamines, polyaminoamides, anhydrides andanhydride-containing copolymers. The addition of polyepoxy resins insmall quantities (<1% by weight) can also improve adhesion to somesubstrates. In this case, however, solid epoxy resins with a molecularweight well above 700 are preferably used in finely ground form so thatthe formulations are still substantially free from epoxy resins, moreespecially those with molecular weights below 700. If tackifiers orprimers are used, the type and quantity used will depend upon thepolymer composition of the adhesive/sealant, upon the required strengthof the cured composition and upon the substrate to which the compositionis applied. Typical tackifying resin (tackifiers), for exampleterpene/phenol resins or resinic acid derivatives, are normally used inconcentrations of 5 to 20% by weight while typical primers, such aspolyamines, polyaminoamides or resorcinol derivatives, are used inconcentrations of 0.1 to 10% by weight.

The compositions according to the invention are preferably free fromplasticizers for the thermoplastic polymer. More particularly, they arefree from phthalic acid esters. However, it may be necessary toinfluence the rheology of the uncured composition and/or the mechanicalproperties of the cured composition by addition of so-called extenderoils, i.e. aliphatic, aromatic or naphthenic oils. However, thisinfluence is preferably exerted through the appropriate choice of thelow molecular weight liquid rubbers or through the use of low molecularweight polybutenes or polyisobutylenes. If extender oils are used, theyare used in quantities of 2 to 15% by weight.

The fillers may be selected from a number of materials, including inparticular chalks, natural ground or precipitated calcium carbonates,calcium/magnesium carbonates, silicates, heavy spar and also carbonblack. Lamellar fillers, for example vermiculite, mica, talcum orsimilar layer silicates, are also suitable as fillers. It may be usefulfor the fillers to be at least partly surface-pretreated. Coating withstearic acid to reduce the moisture introduced and to prevent the curedcomposition from becoming sensitive to moisture have proved to beparticularly useful for the various calcium carbonates or chalks. Inaddition, the compositions according to the invention generally containbetween 1 and 5% by weight of calcium oxide. The total content offillers in the formulation can vary from 10 to 70% by weight and ispreferably in the range from 25 to 60% by weight.

Conventional stabilizers, for example sterically hindered phenols oramine derivatives, may be used to prevent thermal, thermo-oxidative orozone degradation of the compositions according to the invention, thesestabilizers typically being used in quantities of 0.1 to 5% by weight.

Although the rheology of the compositions according to the invention cannormally be brought into the required range through the choice of thefillers and the quantity ratio of the low molecular weight liquidrubbers, conventional rheology aids, for example pyrogenic silicas,Bentones or fibrillated or pulped chopped strands may be added inquantities of 0.1 to 7%. In addition, other conventional auxiliaries andadditives may be used in the compositions according to the invention.

As mentioned at the beginning, a preferred application for theone-component hot-curing adhesive/sealant composition according to theinvention is in white-shell assembly in the car industry, so that thecompositions should cure in 10 to 35 minutes at temperatures of 80 to240° C., temperatures of 160° C. to 200° C. preferably being applied inwhite-shell assembly. A major advantage of the compositions according tothe invention over known paste-form one-component epoxy resin adhesiveslies in their so-called "washing resistance" immediately afterapplication of the adhesives, i.e. they do not require pregelation inthe same way as the above-mentioned epoxy adhesives to be resistant tothe various washing and phosphating baths used in white-shell assembly.The compositions according to the invention have the advantage overhotmelt epoxy adhesives that they need only be gently heated to around30 to 45° C. for pumping and for application, in addition to which theirwetting power for cold substrates is considerably better than that ofepoxy hotmelts by virtue inter alia of their greater inherent tackiness.

EXAMPLES

The following Examples are intended to illustrate the invention withoutlimiting it in any way.

To determine tensile shear strength, 1.5 mm thick strips of a 14 O5steel measuring 25×100 mm were bonded with the adhesives with an overlapof 25×20 mm; the layer thickness of the adhesive was 0.2 mm. The steelstrips had been oiled beforehand with ASTM Oil No. 1, coating weight 3to 4 g/m². Breaking elongation and tear strength were determined on anS2 test specimen according to DIN 53 504, layer thickness 2 mm. Aconventional laboratory tensile testing machine was used for bothtensile tests (rate of advance 50 mm/min.). The adhesives were cured ina laboratory circulating-air oven, cure time: 30 mins. at 180° C.

In an evacuable laboratory kneader, the compositions identified in thefollowing Tables were mixed in vacuo until they were homogeneous. Unlessotherwise indicated, all parts in the Examples are parts by weight.

                  TABLE 1                                                         ______________________________________                                                             Comparison                                                                              Comparison                                                   Example 1                                                                            Example 1 Example 2                                      ______________________________________                                        Polybutadiene, solid (1)                                                                      5.0      5.0       5.0                                        Polybutadiene, liquid (2)                                                                     5.0      5.0       5.0                                        Polybutadiene, liquid (3)                                                                     15.0     15.0      15.0                                       Polybutadiene, liquid (4)                                                                     5.0      5.0       5.0                                        Zinc oxide, active                                                                            4.0      4.0       4.0                                        Sulfur, powder  7.0      5.0       7.0                                        Dibenzothiazyl disulfide                                                                      5.0      5.0       5.0                                        (MBTS)                                                                        Polyvinyl acetate, powder (5)                                                                 10.0     --        --                                         Calcium carbonate                                                                             41.0     53.0      51.0                                       Calcium oxide   2.5      2.5       2.5                                        Antioxidant     0.5      0.5       0.5                                        Tensile shear strength                                                                        18.3 MPa 8.2 MPa   14.7 MPa                                   Breaking elongation                                                                           26.0%    57.3%     4.96%                                      Tear strength   16.5 MPa 7.0 MPa   14.5 MPa                                   ______________________________________                                         (1) Cis1,4 at least 98%, Mooney viscosity 48 (ML4100)                         (2) MW about 1800, cis1,4 about 72%                                           (3) MW about 1800, vinyl about 40-50%                                         (4) Polybutadiene/maleic anhydride adduct, MW about 1700                      (5) EVA copolymer, Tg about 23° C.                                

                  TABLE 2                                                         ______________________________________                                                                           Comparison                                           Example 2                                                                            Example 3                                                                              Example 4                                                                              Example 1                                  ______________________________________                                        Polybutadiene,                                                                            5.0      5.0      5.0    5.0                                      solid (1)                                                                     Polybutadiene,                                                                            5.0      5.0      5.0    5.0                                      liquid (2)                                                                    Polybutadiene,                                                                            15.0     15.0     15.0   15.0                                     liquid (3)                                                                    Polybutadiene,                                                                            5.0      5.0      5.0    5.0                                      liquid (4)                                                                    Zinc oxide, active                                                                        4.0      4.0      4.0    4.0                                      Sulfur, powder                                                                            5.0      5.0      5.0    5.0                                      Dibenzothiazyl                                                                            5.0      5.0      5.0    5.0                                      disulfide (MBTS)                                                              Polyvinyl chloride (5)                                                                    10.0     --       --     --                                       Styrene     --       10.0     --     --                                       methacrylate (6)                                                              Polymethyl  --       --       10.0   --                                       methacrylate (7)                                                              Calcium carbonate                                                                         43.0     43.0     43.0   53.0                                     Calcium oxide                                                                             2.5      2.5      2.5    2.5                                      Antioxidant 0.5      0.5      0.5    0.5                                      Tensile shear strength                                                                    9.4 MPa  9.8 MPa  11.9 MPa                                                                             8.2 MPa                                  Breaking elongation                                                                       46.7%    34.1%    29.5%  57.3%                                    Tear strength                                                                             8.2 MPa  7.0 MPa  9.9 MPa                                                                              7.0 MPa                                  ______________________________________                                         (1) Cis1,4 at least 98%, Mooney viscosity 48 (ML4100)                         (2) MW about 1800, cis1,4 about 72%                                           (3) MW about 1800, vinyl about 40-50%                                         (4) Polybutadiene/maleic anhydride adduct, MW about 1700                      (5) Emulsion PVC, K value 70                                                  (6) Styrene copolymer according to DEA-40 34 725, 7.5% methacrylic acid       (7) PMMA containing copolymerized vinyl imidazole                        

In the tensile shear strength test, cohesive failure was observed withall test specimens.

The only plate thicknesses available for determining adhesion behavioron galvanized steel were the plate thicknesses of 0.8 mm typically usedin the automotive industry. However, high-strength structural adhesivesof the present examples are already in the strength range of these thinsteel plates so that the adhesion behavior on these substrates couldonly be evaluated by a qualitative peel test. To this end, the steelplates were oiled with ASTM Oil No. 1, coated with the adhesive,oven-cured as described above and then evaluated in a manual peel test.The following substrates were tested: electrolytically galvanized,hot-dip galvanized, galvanized and phosphated and galvannealed steelplates. Cohesive failure was observed in every case.

As can be seen from a comparison of Comparison Example 1 with ComparisonExample 2, the tensile shear strength or tear strength of therubber-based adhesives according to the prior art can be significantlyincreased solely through a higher content of sulfur, although at thesame time there is a drastic reduction in breaking elongation. Theaddition of polyvinyl acetate copolymer (Example 1) in accordance withthe invention produces a significant increase in tensile shear strengthbut, at the same time, keeps breaking elongation at a high level (26%).As can be seen by comparing Comparison Example 1 (no addition ofthermoplastic powder) with Examples 2 to 4, tensile shear strength canbe significantly increased by this addition, despite a low sulfurcontent, through the addition of the various thermoplastic powders withonly a very slight reduction in breaking elongation.

What is claimed is:
 1. A one-component adhesive compositionsubstantially free of epoxy resin and consisting essentially of:(a) atleast one liquid rubber having a molecular, weight below 20,000 presentin an amount of between 5% and 50% by weight, (b) at least onethermoplastic polymer powder having an average particle size below 1 mmpresent in an amount of between 2% and 20% by weight, said thermoplasticpolymer powder being selected from the group consisting of vinyl acetatehomopolymers, vinyl acetate copolymers, ethylene/vinyl acetatecopolymers, vinyl chloride homopolymers, vinyl chloride copolymers,styrene homopolymers, styrene/methacrylic acid copolymer (meth)acrylatehomopolymers, (meth)acrylate copolymers, polyvinyl acetals, and mixturesthereof, (c) a vulcanization system for said composition comprised of avulcanizing agent selected from the group consisting of elementalsulfur, thiuram disulfides, organic peroxides, polyfunctional amines,quinones, p-benzoquinone dioxime, p-nitrosobenzene, dinitrosobenzene andmixtures thereof, (d) at least one filler present in an amount ofbetween 10% and 70% by weight, all weights being based on the weight ofsaid composition;said composition being curable at a temperature ofbetween 80° C. and 240° C., and when cured, having a breaking elongationaccording to DIN 53504 of more than about 15% and a tensile shearstrength of at least 9.4 mPa and forming a permanent adhesive bond to ametal surface.
 2. The composition as claimed in claim 1, furtherconsisting essentially of at least one solid rubber in a quantity ofabout 1.5% by weight to about 9% by weight, based on the composition asa whole.
 3. The composition as claimed in claim 1, further consistingessentially of at least one solid rubber in a quantity of about 4% byweight to about 6% by weight, based on the composition as a whole. 4.The composition as claimed in claim 1, wherein said vulcanization systemis comprised of sulfur, at least one organic vulcanization accelerator,and at least one zinc compound.
 5. The composition as claimed in claim1, wherein said vulcanization system comprises about 4% by weight toabout 15% by weight of powder-form sulfur, about 2% by weight to about8% by weight of one or more organic accelerators and about 1% by weightto about 8% by weight of one or more zinc compounds, the percentages byweight being based on the composition as a whole.
 6. The composition asclaimed in claim 5 wherein the powder-form sulfur comprises about 5% byweight to about 10% by weight of the composition as a whole.
 7. Thecomposition as claimed in claim 5 wherein the organic acceleratorscomprise about 3% by weight to about 6% by weight of the composition asa whole.
 8. The composition as claimed in claim 5 wherein the zinccompounds comprise about 2% by weight to about 6% by weight of thecomposition as a whole.
 9. The composition as claimed in claim 5,wherein zinc oxide is one of the zinc compounds.
 10. The composition asclaimed in claim 1, wherein said thermoplastic polymer powder has anaverage particle size below about 350 microns.
 11. The composition asclaimed in claim 1, wherein said thermoplastic polymer powder has anaverage particle size of between 20 and 100 microns.
 12. The compositionas claimed in claim 1, wherein said composition is substantially freefrom plasticizers for the thermoplastic polymer.
 13. The composition asclaimed in claim 1, further containing an ingredient selected from thegroup consisting of rheology, aids, extender oils, primers, tackifiers,antiagers and mixtures thereof.
 14. A process for the production of thecomposition claimed in claim 1, comprising the step of high-shear mixingof the components.
 15. In a process comprising a step of adhering metalcomponents with a one-component structural adhesive, wherein theimprovement comprises adhering said metal components with thecomposition of claim
 1. 16. The improved process claimed in claim 15wherein the process comprises white-shell assembly in car manufacture.17. A process for bonding metal parts or for sealing joints betweenmetal parts, comprising the steps of:coating at least one surface of anat least one first part with the composition claimed in claim 1; fittingtogether the at least one first part with an at least one second part tobe joined; and heating the fitted parts to a temperature of between 80°C. and 240° C., wherein said heating cures said composition and joinssaid parts.
 18. The process claimed in claim 17 further comprising thestep of mechanically joining the fitted parts before the step of heatingthe fitted parts.
 19. A process for coating structural componentscomprising the steps of:spraying or extruding the composition claimed inclaim 1 onto the surface of a part; and heating the coated part to atemperature of between 80° C. and 240° C., wherein said heating of saidpart cures the composition.
 20. A process for coating, bonding orsealing structural components comprising the steps of:extruding thecomposition claimed in claim 1 in the form of a film, cord or tape,applying said extruded composition to at least one first structuralcomponent; and heating the structural component or components to atemperature of between 80° C. and 240° C.
 21. The process claimed inclaim 20 further comprising the step of fitting together the at leastone structural component to at least one second structural componentbefore said heating.
 22. The composition as claimed in claim 1, having atensile shear strength of at least 15 mPa.
 23. The composition asclaimed in claim 1, wherein the liquid rubber has a molecular weight offrom 900 to 10,000.
 24. The composition as claimed in claim 1, whereinthe liquid rubber is selected from the group consisting ofpolybutadienes, polybutenes, polyisobutylenes, polyisoprenes,styrene/butadiene copolymers, butadiene/acrylonitrile copolymers, andmixtures thereof.
 25. The composition as claimed in claim 1, wherein theliquid rubber contains functional groups selected from the groupconsisting of hydroxy, amino, carboxyl, carboxylic anhydride, epoxy andcombinations thereof.
 26. The composition as claimed in claim 1containing at least two liquid rubbers, one liquid rubber having a highpercentage of cis-1,4-double bonds and another liquid rubber having ahigh percentage of vinyl double bonds.
 27. A one component adhesivecomposition substantially free of epoxy resin and consisting essentiallyof:(a) at least one liquid rubber having a molecular weight of from 900to 10,000 present in an amount of between 5% and 50% by weight, saidliquid rubber being selected from the group consisting ofpolybutadienes, polybutenes, polyisobutylenes, polyisoprenes,styrene/butadiene copolymers, butadiene/acrylonitrile copolymers, andmixtures thereof; (b) at least one thermoplastic polymer powder havingan average particle size below 350 μm present in an amount of between10% and 15% by weight, said thermoplastic polymer powder being selectedfrom the group consisting of vinyl acetate homopolymers, vinyl acetatecopolymers, ethylene/vinyl acetate copolymers, vinyl chloridehomopolymers, vinyl chloride copolymers, styrene homopolymers, styrenecopolymers, (meth)acrylate homopolymers, (meth)acrylate copolymers,polyvinyl acetals, and mixtures thereof; (c) a vulcanization systemcomprised of 4% to 15% by weight elemental sulfur, 2% to 8% by weight ofone or more organic accelerators, and 1% to 10% by weight of one or morezinc compounds; (d) at least one filler present in an amount of 25% to60% by weight; (e) at least one stabilizer present in an amount of 0.1%to 5% by weight; (f) at least one solid rubber present in an amount of1.5% to 9% by weight, all weights being based on the weight of saidcomposition;said composition being curable at a temperature of between160° C. and 200° C., and, when cured, having a breaking elongationaccording to DIN 53504 of more than about 20% and a tensile shearstrength of at least 15 mPa and forming a permanent adhesive bond to ametal surface.
 28. The composition as claimed in claim 27, wherein atleast one solid rubber is selected from the group consisting ofpolybutadienes, styrene/butadiene rubbers, butadiene/acrylonitrilerubbers, isoprene rubbers, butyl rubbers, and polyurethane rubbers. 29.The composition as claimed in claim 27, wherein at least one solidrubber is a polybutadiene rubber having a percentage of cis-1,4-doublebonds above 95%.
 30. The composition as claimed in claim 27, wherein atleast one thermoplastic polymer has an average particle size from 20 μmto 100 μm and is selected from the group consisting of polyvinylacetates, ethylene/vinyl acetate copolymers, polyvinyl chlorides,polymethyl methacrylates, and styrene methacrylates.
 31. The compositionas claimed in claim 27, wherein at least one liquid rubber containsfunctional groups selected from the group consisting of hydroxyl groups,carboxylic anhydride groups, and combinations thereof.
 32. Thecomposition of claim 27 containing at least two liquid rubbers, oneliquid rubber having a high percentage of Cis-1,4-double bonds andanother liquid rubber having a high percentage of vinyl double bonds.33. The composition of claim 27, wherein from 1% to 5% by weight calciumoxide is used as one of the fillers.
 34. The composition of claim 27further containing at least one ingredient selected from the groupconsisting of rheology aids, tackifiers, extender oils, primers, andmixtures thereof.